Nationality: United StatesExecutive summary: ENIAC, BINAC, and UNIVAC I computers

John William Mauchly taught physics and electrical engineering, and collaborated with his student, John Presper Eckert, to design and construct a general-purpose calculating device called ENIAC (Electronic Numerical Integrator and Computer). In his 1942 paper proposing the project, Mauchly introduced the concept of "computer programming" by coining the concept "to program" as a verb.

Completed in 1945 and put into service the following year, ENIAC cost $486,804 to build, and it was classified top-secret, code-named Project PX, with expenses paid by the federal government and tests conducted at the Aberdeen Proving Ground in Maryland. The machine weighed some thirty tons, all input and output was through IBM punch cards, and calculations would fail whenever any of its 17,468 vacuum tubes burned out, but it offered a breathtaking improvement in speed and ability over any other machine of its era.

In 1941, however, as these ideas were forming in his mind, Mauchly visited the lab of John Atanasoff at Iowa State University, and scrutinized Atanasoff's ABC Computer. In a 1973 patent lawsuit, a court determined that Atanasoff, not Eckert and Mauchly, deserved credit for the invention of the digital computer, though Mauchly always maintained that he had been unimpressed with Atanasoff's machine and its comparatively limited abilities. Credit is certainly due to all three scientists, but Atanasoff's machine was far simpler and performed a single function, while ENIAC's programming was general-purpose and variable, making it a true general-purpose computer.

Mauchly and Eckert founded the Eckert-Mauchly Computer Company in 1946, and went on to design and build UNIVAC (Universal Automatic Computer), the first computer used for commercial applications. His father, physicist Sebastian Jacob Mauchly, was the director of the Carnegie Institution of Washington's Department of Terrestrial Magnetism, and conducted research in electricity and earth currents.